Study by DGHI's Jim Zhang and Colleagues as posted by Brigitte Perreault POLLUTION CONTROL MEASURES CREATED A “NATURAL EXPERIMENT”

Exposure to
high levels of pollution can have a significant impact on fetal growth

And development.
That’s the conclusion of a recent study in Environmental Health Perspectives,
co-authored by Jim Zhang, professor of global and environmental

health.

The study found
that women who were pregnant during the 2008 Beijing Olympics, when pollution
levels were reduced by the Chinese government, gave birth to children with
higher birth weights compared to those who were pregnant before and after the
games.

“The results of
this study demonstrate a clear association between changes in air pollutant concentrations
and birth weight,” said lead author David Rich, an epidemiologist at the
University of Rochester Medical Center. “These findings not only illustrate one
of the many significant health consequences of pollution, but also demonstrate
that this phenomenon can be reversed.”

In the months
leading up to and during the 2008 Beijing Olympics and Paralympics, the Chinese
government launched a series of aggressive measures to improve the city’s
chronic and notoriously poor air quality. These measures included an aggressive
program to curtail pollution by implementing strict restrictions on automobile
and truck use, closing factories, halting construction projects and seeding
clouds to induce rainfall. These controls—which were subsequently relaxed upon
completion of the games—produced a significant decrease in the concentrations
of particulate and gaseous air pollution for a 6-7 week period during the
Olympic games,including a 60 percent reduction in sulfur dioxide, a 48 percent
reduction in

carbon
monoxide, a 43 percent reduction in nitrogen dioxide, and a reduction in particles
smaller than 2.5 microns in diameter.

These measures
created a unique “natural experiment”
for scientists to study the impact of pollution on human health. A prior study by
this group, which was also conducted in conjunction with the Beijing Olympics,
demonstrated that pollutions levels were linked to physiological changes that
increase risk for cardiovascular disease, and that these same air pollution
reductions resulted in improvements in several risk factors.

RESEARCHERS LOOKED AT LAST MONTH OF PREGNANCY, A KEY FETAL GROWTH
PERIOD

The
researchers compiled information from 83,672 term births (37 to 42 weeks
gestational age at birth) to mothers in four urban districts in Beijing. They
compared birth weights for mothers whose eighth month of pregnancy occurred
during the 2008 Olympics/Paralympics with those whose eighth month of pregnancy
occurred at the same time of year in the years before (2007) and after (2009)
the games when pollution levels were at their normally higher levels. They
found that the babies born in 2008 were on average 23 grams larger than those
in 2007 and

2009. Late
pregnancy is a particularly important period of fetal growth, as during this
time

The fetus experiences
the greatest amount of physical growth, and the development of the central nervous,
car diovascular, and musculoskeletal systems accelerates. The study suggests
that pollution may be interfering with this period of development.

STUDY SHOWS EVEN SHORT-TERM MEASURES LEAD TO BENEFITS

While the
biological mechanism by which exposure to pollution causes lower birth weights
are not fully understood, the scientists speculate that several factors could
play a role, including maternal inflammation, altered placental function, and
reduced nutrient delivery to the fetus,

which may
impede fetal growth. “While Beijing’s pollution is particularly noteworthy,
many of the world’s other cities face similar air quality problems,” said
Zhang. “This study shows that pollution controls—even short-term ones—can have
positive public health benefits.”

The study was funded by the National Institute of Environmental Health Sciences.

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